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<div class="titlepage"><div><div><h3 class="title">
<a name="boost_asio.reference.OperationState"></a><a class="link" href="OperationState.html" title="Operation state concept">Operation state
      concept</a>
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<pre class="programlisting">template&lt;class O&gt;
  concept operation_state =
    destructible&lt;O&gt; &amp;&amp;
    is_object_v&lt;O&gt; &amp;&amp;
    requires (O&amp; o) {
      { execution::start(o) } noexcept;
    };
</pre>
<p>
        An object whose type satisfies <code class="computeroutput">operation_state</code> represents the
        state of an asynchronous operation. It is the result of calling <code class="computeroutput">execution::connect</code>
        with a <code class="computeroutput">sender</code> and a <code class="computeroutput">receiver</code>.
      </p>
<p>
        <code class="computeroutput">execution::start</code> may be called on an <code class="computeroutput">operation_state</code>
        object at most once. Once <code class="computeroutput">execution::start</code> has been invoked,
        the caller shall ensure that the start of a non-exceptional invocation of
        one of the receiver's completion-signalling operations strongly happens before
        [intro.multithread] the call to the <code class="computeroutput">operation_state</code> destructor.
      </p>
<p>
        The start of the invocation of <code class="computeroutput">execution::start</code> shall strongly
        happen before [intro.multithread] the invocation of one of the three receiver
        operations.
      </p>
<p>
        <code class="computeroutput">execution::start</code> may or may not block pending the successful
        transfer of execution to one of the three receiver operations.
      </p>
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<td align="right"><div class="copyright-footer">Copyright © 2003-2021 Christopher
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        Distributed under the Boost Software License, Version 1.0. (See accompanying
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